drm/amdkfd: fix amdkfd use-after-free GP fault

Fix GP fault caused by dev_info() reference to a struct device*
after the device has been freed (use after free).
kfd_chardev_exit() frees the device so 'kfd_device' should not
be used after calling kfd_chardev_exit().
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/gpu/drm/amd/amdkfd/kfd_module.c

@@ -24,6 +24,7 @@
 #include <linux/sched.h>
 #include <linux/moduleparam.h>
 #include <linux/device.h>
+#include <linux/printk.h>
 #include "kfd_priv.h"
 
 #define KFD_DRIVER_AUTHOR	"AMD Inc. and others"
@@ -132,7 +133,7 @@ static void __exit kfd_module_exit(void)
 	kfd_process_destroy_wq();
 	kfd_topology_shutdown();
 	kfd_chardev_exit();
-	dev_info(kfd_device, "Removed module\n");
+	pr_info("amdkfd: Removed module\n");
 }
 
 module_init(kfd_module_init);